Oral Pathogens

Researchers at Tampere University have shown for the first time that the cerebral emboli; but stroke patients contain DNA from oral pathogens. The research article has been published in the Journal of American Heart Association. Chronic infections have been report to be risk factors for both coronary heart disease and ischemic stroke.

DNA of oral bacteria, mainly from the viridans streptococci group; has been detect in coronary thrombus aspirates of myocardial infarction and cerebral aneurysms. Viridans streptococci are knowing to cause infective endocarditis; and possess thrombogenic properties. We studied the presence of oral bacterial DNA in thrombus aspirates of patients; with acute ischemic stroke treated with mechanical thrombectomy.

The researchers analysed thrombus aspirates, which neurointerventional radiologists; removed from 75 stroke patients as part of emergency treatment. But the samples were studied by duplicating bacterial DNA, showing that 79 % of the aspirates; contained DNA from bacteria that came from the teeth.

Coronary artery stenoses

The study is part of a research project at Tampere University, which for ten years has been investigating the effects of bacterial infection in the development of cardiovascular diseases. The research group has previously shown that the same odontogenic bacteria; but are present in the coronary artery stenoses of patients who have suddenly died.

The thrombus aspirates and arterial blood of myocardial infarction patients; but ruptured cerebral aneurysms and the thrombus aspirates of patients with lower limb arterial and venous thrombosis. Cerebral artery thrombosis causes 87 % of strokes. Most thrombi originate in carotid artery stenoses from where they travel to block cerebral circulation.

Health damage or death

The results showed that a large amount of DNA from streptococcus viridans; but normal bacteria in the mouth was finding in cerebral thrombi compare with normal blood samples from the same patients. In the oral cavity, streptococci are harmless, but when entering circulation; they might cause, among other things, infections of the cardiac valves. But the streptococcus bacteria can directly bind to various platelet receptors, making the patient more prone to blood clots.

The research shows that oral health and good dental hygiene are of much greater importance; but to health than previously known, and that untreated dental infections can cause serious health damage or even death.

Thrombus aspirates and arterial blood were taking from 75 patients (69% men; mean age, 67 years) with acute ischemic stroke. The presence of Streptococcus species, mainly the Streptococcus mitis group; belonging to viridans streptococci as well as Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans; in samples were determine using a quantitative polymerase chain reaction with specific primers and probes.

Bacterial DNA

But the relative amount of bacterial DNA in a sample was determine; with the comparative threshold cycle method. Bacterial DNA was detect in 84% (n=63) of aspired thrombi; and 16% (n=12) of samples were considered bacterial DNA negative.

DNA of Streptococcus species, mainly the S mitis group, was found in 79% (n=59) of samples. The median relative amount of Streptococcus species DNA; was 5.10‐fold higher compared with the control blood samples from the same patients. All thrombi were negative for both P gingivalis and A actinomycetemcomitans.

But this is the first study showing the common presence of bacterial DNA from viridans streptococci; in aspired thrombi of patients with acute ischemic stroke. But Streptococcal bacteria, mostly of oral origin, may contribute to the progression and thrombotic events of cerebrovascular diseases.